The present invention relates generally to radar antennas, and more specifically the invention pertains to a microwave corrugated horn antenna system which uses a magnetic coating to enhance its radiation pattern.
The combination of a parabolic or partially parabolic reflector illuminated by a horn antenna is one of the earliest antenna system arrangements employed in radar systems for the generation of a highly directive beam in space, and accordingly is extensively described in the technical literature. The text "Antenna Engineering Handbook," Henry Jasik, Editor (McGraw-Hill 1961) provides an overview of the art in that respect.
Exemplary examples of conical antenna systems are described in the following U.S. Patents, the disclosures of which are incorporated herein by reference:
U.S. Pat. No. 4,477,816 issued to Cho;
U.S. Pat. No. 4,792,814 issued to Ebisui;
U.S. Pat. No. 3,631,502 issued to Peters et al; and
U.S. Pat. No. 4,928,109 issued to Bonebright et al.
The Cho and Peters et al. patents disclose corrugated antenna feed horn systems that could be improved by the present invention. The Ebisui reference discloses a conical horn antenna which uses plural modes of electromagnetic waves. The Bonebright et al. reference discloses a non-magnetic electrically conducting radiating horn antenna.
Also of interest are publications entitled "Magnetically Coated Horn for Low Sidelobes and Low Cross-Polarization," IEE Proceedings, Vol. 136, Pt. H. No. Apr. 2, 1989, pages 132 through 138, and "Design and Performance of the Magnetic
Hybrid-Mode Horn," IEEE Transactions on Antennas and Propagation, Vol. 37, No. Nov. 11, 1989, pages 1407 through 1414. These articles suggest a use of magnetic coatings on antennas to enhance the circular polarization radiation performance. These articles are specifically incorporated herein by reference.
Many corrugated horn antennas have large weight and stringent mechanical tolerances, and are therefore impractical or expensive in most application. The present invention overcomes these limitations. As compared with the previously reported coated horn system, the present invention overcomes the deficiencies of high gain loss and poor patterns.